In 2016 a work friend of mine was approached by someone they knew on the Westford Fire and Water Board, who knew another guy, who was thinking of bringing fiber internet to a section or rural Vermont. The rest is history. We started with nothing, and I slowly started teaching myself all about networking. It was also around this time that I was exposed to Docker - this was the perfect test to start spinning up services. In the end using almost entirely open-source software, some customer solutions of mine, and off the shelf networking equipment - we have an ecosystem that requires very little maintenance that runs our company. We are at over 750 customers so far.
We gave some paid vendor solutions a try in the beginning, but it was a disaster and just a waste of money. It was easier and cleaner to just set the stuff up myself. We are using normal off the shelf Mikrotik equipment for the routing and switching. For the last mile (or 12), we are using Ubiquiti UFiber equipment. Ubiquiti is a technically a vendor - but we run everything on our own systems and have complete control of all the data - for free still. Amazing. Since 2018, we've had nothing but great things to say about that equipment. It's cheap too.
Like the hardware - we also looked at some vendor software packages for ISPs. It was all total crap at the time. The only companies we pay for software are DigitalOcean for remote VMs, Google Workspace, and QuickBooks. Open source tools like Zabbix, Grafana, PostGIS, ACS, and homemade solutions allow us to keep a constant feed on all our systems and build maps of our network in the field.